What to do with two Shivas?

[DeanP]

Hi All:

I have a 95l vented Shiva now.

Last fall, I got three Shivas from Thomas and sold them to three friends, one has decided that the "box" is going to be too big for the "waf", so he is selling it. So now I thought that maybe I should buy it back and do something with.
Question is, should I:
Build another 95l vented and have two in the same room; or
build another type of box; or
ignore it and maybe somebody else will buy it?

Any suggestions?

BTW my room is 14' * 18'* 9' high ceilings.

[cdwitmer]

Some possibilities:

You can use them in isobaric configuration to enable use with a box 50% smaller; there will also be some reduction of distortion although I don't know if you will be able to hear the difference.

You can build another sub enclosure similar to the one you have now and use some sort of a rigid connection system to connect the enclosures so the drivers fire facing one another. If you previously had troubles with your sub tending to "walk" around the room, this will put an end to it, as the vibrations will cancel out. No need to worry about cancellation of the music signals that the subs put out; at those frequencies they might as well be a single driver.

Build an infinite baffle sub; pairs of drivers are usually desireable for just the sort of vibration cancellation described above.

[Jam_Master_J]

Hey,
A local guy is selling two Shivas cheap I thought I'd get in on this too.

I'm building the ported M8 MTM design soon and am looking at subs to fill in the bottom end. They'll be used in a small room so huge output isn't nescessary. There won't be many options on their placement and looks are important so I think dipoles are kind of ruled out? I was thinking maybe two sealed ones, that way they can be stacked for output or placed separately to even out bass response. I'd like to cross them over fairly low, maybe 50 Hz or so. Crazy entension isn't needed, 25Hz should be deep enough. These will only be used for music.

[cdwitmer]

I have not familiarized myself with the ported M8 MTM design, but if you have access to two Shivas to use as subs, you might consider going to a non-ported design for the main speakers. If you can get to below 100Hz with your main speakers in a non-ported design (I should think that would not be difficult), you can probably cross over to the subs more easily with a sealed enclosure design. And you might want to go with sealed subs too.

If you think there might be times when you might want to run the main speakers only, without the subs, you might go with a ported enclosure design in your main speakers after all. Then, when you do run the subs, try to cross over well above the port frequency using a steep crossover. That way your main speaker ports will be mostly silent when the subs are running. You don't need your main speaker ports AND the subs reduplicating each other's efforts, so to speak. One of the advantages of the approach I just outlined is that the power handling abililty of your main speakers' woofers will go way up, as the limiting factor is always the bottom end power handling. If you are crossing over well above the woofers' Fo, you can put a lot more juice in them without fear of damaging them. (Of course the tweeter's power handling will remain unchanged by all this.)

[ThomasW]

If you're going to always use the MTM cluster with a Shiva on the bottom. Make your life simple and build the MTM sealed. Then use a standard 80Hz XO for the sub.

[Jam_Master_J]

Since I already have the ported design planned (ie cuts planned etc...) perhaps I'll just build the ported and experiment with plugging the port. I don't think the porting will make things much more difficult. You mention it being easier to blend if the MTMs are also sealed, is this because the sealed will have a natural roll-off not seen with the ported version?

It might be a couple months before I do the Shivas so I would be running the speakers in 2-channel for a while. The size difference isn't significant to me.

If I did decide to seal the MTMs and go with the Shivas, would it be worth my time to set up stereo subs rather than summing all the LF signal?

If I like the MTMs enough without a sub I may just throw the shivas in the corner with my Tempest for HT.

[cdwitmer]

Particularly if you have a sufficiently steep XO, you probably won't notice a difference with or without summing of the L and R signals, assuming you are crossing at 80Hz. If you go with a (relatively shallow) 12dB or 6dB per octave XO, you might prefer to have the L and R signals separate.

If I recall correctly, some people have good results sealing ports with screw-tightenable rubber plugs that plumbers use. Yeah, the natural -6dB/octave rolloff of a sealed enclosure can be useful, although the frequency is determined by the physical properties of the driver and enclosure. So it might be above or below 80Hz. If the natural frequency is inconvenient, you can always get an electronic XO to chop it off at a higher frequency.